The big downside of this Tor Mass Market edition is the 104mm width. There are >750 pages, so the small size makes it uncomfortable to read. Go for the Gollancz or the Tor Trade edition instead.
Content: this collection collects all of the shorter Cosmere works (as of publication date) in one volume. Novellas: Emperor's Soul – an excellent standalone, from the same universe as Elantris, Mistborn: Secret History – a Mistborn novella with quite a revelation, Edgedancer – a Stormlight novella. All of these are also available standalone for roughly the same price as this collection. There are a handful of other shorts – 6th of the Dusk is the standout – and an excerpt of the White Sands graphic novel. It's amazing value.